Expose Zones.

tests/lib/async/catch_errors13_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:async_helper/async_helper.dart';
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'catch_errors.dart';
 
 main() {
   asyncStart();
+  Completer done = new Completer();
+
   var events = [];
   // Work around bug that makes runAsync use Timers. By invoking `runAsync` here
   // we make sure that asynchronous non-timer events are executed before any
   // Timer events.
   runAsync(() { });
 
   // Test that errors are caught by nested `catchErrors`. Also uses `runAsync`
   // in the body of a Timer.
   catchErrors(() {
     events.add("catch error entry");
     catchErrors(() {
       events.add("catch error entry2");
       Timer.run(() { throw "timer error"; });
       new Timer(const Duration(milliseconds: 50),
                 () {
                      runAsync(() { throw "runAsync"; });
                      throw "delayed error";
                    });
-    }).listen((x) { events.add(x); })
-      .asFuture()
-      .then((_) => events.add("inner done"))
-      .then((_) { throw "inner done throw"; });
+    }).listen((x) {
+      events.add(x);
+      if (x == "runAsync") {
+        throw "inner done throw";
+      }
+    });
     events.add("after inner");
     Timer.run(() { throw "timer outer"; });
     throw "inner throw";
   }).listen((x) {
       events.add(x);
+      if (x == "inner done throw") done.complete(true);
     },
-    onDone: () {
+    onDone: () { Expect.fail("Unexpected callback"); });
+
+  done.future.whenComplete(() {
+    // Give callbacks time to run.
+    Timer.run(() {
       Expect.listEquals([
                          "catch error entry",
                          "catch error entry2",
                          "after inner",
                          "main exit",
                          "inner throw",
                          "timer error",
                          "timer outer",
                          "delayed error",
                          "runAsync",
-                         "inner done",
                          "inner done throw"
                          ],
                          events);
       asyncEnd();
     });
+  });
   events.add("main exit");
 }